Haemophilus influenzae infection overview
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Haemophilus influenzae infection Main page |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Infection with the bacterium Haemophilus influenzae type b (Hib) can result in meningitis and other severe infections (e.g., pneumonia, bacteremia, cellulitis, septic arthritis, and epiglottitis) primarily among infants and children <5 years of age.
Pathophysiology
Haemophilus influenzae, formerly called Pfeiffer's bacillus or Bacillus influenzae, is a non-motile Gram-negative coccobacillus first described in 1892 by Richard Pfeiffer during an influenza pandemic. It is generally aerobic, but can grow as a facultative anaerobe. H. influenzae was mistakenly considered to be the cause of the common flu until 1933, when the viral etiology of the flu became apparent. Still, H. influenzae is responsible for a wide range of clinical diseases. Transmission is by direct contact with respiratory droplets from nasopharyngeal carrier or case patient.
Epidemiology and Demographics
During 1980-1990, incidence was 40-100/100,000 children < 5 years old in the United States. Due to routine use of the Hib conjugate vaccine since 1990, the incidence of invasive Hib disease has decreased to 1.3/100,000 children. However, Hib remains a major cause of lower respiratory tract infections in infants and children in developing countries where vaccine is not widely used.
Risk Factors
Infants and young children, household contacts, and day care classmates are at higher risk of acquiring Haemophilus influenza serotype B infection.
Prognosis
3%-6% of cases are fatal; up to 20% of surviving patients have permanent hearing loss or other long-term sequelae.
Diagnosis
History and Symptoms
Before the availability of the Haemophilus influenzae serotype b (Hib) conjugate vaccine in the United States and other industrialized countries, more than one-half of Hib cases presented as meningitis with fever, headache, and stiff neck. The remainder presented as cellulitis, arthritis, or sepsis. In developing countries, Hib is still a leading cause of bacterial pneumonia deaths in children.
Treatment
Medical Therapy
Specific parenteral antibiotic treatment is necessary for invasive Hib disease, and immediate airway stabilization is necessary for epiglottitis. A 4-day course of rifampin eradicates Hib carriage from the pharynx in approximately 95% of carriers.
Primary Prevention
Haemophilus Influenzae Type b (Hib) Vaccine
Future and Investigational Therapies
Evaluating the characteristics of Hib vaccines associated with prevention of carriage and invasive disease will facilitate application of this technology to development of conjugate vaccines for other organisms with polysaccharide capsules (such as the meningococcus, pneumococcus, and group B streptococcus). Further evaluation of herd immunity effects may lead to insight into vaccination strategies that optimize protection against invasive disease and transmission of Hib organisms.